Initial commit

lib/jsmodbus/handler/client/ReadDiscreteInputs.js

@@ -0,0 +1,62 @@
+'use strict';
+
+const Stampit = require('stampit');
+const Put     = require('put');
+
+
+module.exports = Stampit()
+    .init(function () {
+        const FC = 2;
+
+        let init = () => this.addResponseHandler(FC, onResponse);
+
+        let onResponse = (unitId, pdu, cb) => {
+            let fc = pdu.readUInt8(0);
+
+            if (fc !== FC) {
+                cb(`ReadDiscreteInputs: Invalid FC ${fc}`);
+            } else {
+                let byteCount   = pdu.readUInt8(1);
+                let counter = 0;
+                let resp = {
+                    unitId,
+                    fc:         fc,
+                    byteCount:  byteCount,
+                    payload:    pdu.slice(2),
+                    data:       []
+                };
+
+                for (let i = 0; i < byteCount; i++) {
+                    let h = 1, cur = pdu.readUInt8(2 + i);
+                    for (let j = 0; j < 8; j+=1) {
+                        resp.data[counter] = (cur & h) > 0 ;
+                        h = h << 1;
+                        counter += 1;
+                    }
+                }
+
+                cb && cb(null, resp);
+            }
+        };
+
+        this.readDiscreteInputs = (unitId, start, quantity) => {
+            return new Promise((resolve, reject) => {
+                if (quantity > 2000) {
+                    return reject('quantity is too big');
+                }
+
+                let pdu = Put().word8be(FC).word16be(start).word16be(quantity).buffer();
+
+                this.queueRequest(unitId, FC, pdu, (err, resp) => {
+                    if (err) {
+                        reject(err);
+                    } else {
+                        resolve(resp);
+                    }
+                });
+            });
+        };
+
+        init();
+    
+    });